The present invention relates in general to a mechanism for registering sheets, for example transported seriatim along a travel path, and more particularly, to a sheet registration mechanism which aligns individual sheets in a plurality of orthogonal directions (e.g., cross-track, in-track, and skew directions relative to the sheet travel path).
In conventional reproduction apparatus, such as printers and copier/duplicators, for example, information is reproduced on receiver members. Typically, the receiver members are cut sheets of plain paper or transparency material. Such receiver member material is transported through the reproduction apparatus in association with various process elements of the reproduction apparatus to have an information reproduction formed thereon. It is important in forming the desired information reproduction that the association of the receiver member be accurately registered relative to the process elements to generate a reproduction which is acceptable to the user.
In recent advanced reproduction apparatus, a method of operation has been provided wherein multiple images can be sequentially placed on a single receiver member. For example, supplemental information can be added to base information to be copied. The supplemental information may be, for example, of a different color from the base information so that the supplemental information stands out on the reproduction. Alternatively, the supplemental information may be a highlight strip overlying the base information to accentuate a portion of the base information. In such instances of placing multiple sequential images on a receiver member, alignment of the receiver member as it travels on each pass through the reproduction apparatus is even more critical than it is when only one information image is to be placed on the receiver member.
In order to accomplish desired registration of the receiver member, the reproduction apparatus transport includes various mechanisms acting on the receiver member to align the member, moving along the transport path, in a plurality of orthogonal directions, at various points throughout the path. Such mechanisms may include, for example, friction roller assemblies or drive belts associated with guides and gates. While such arrangements are generally effective in aligning a transported receiver member, extreme care is required in handling the receiver member to prevent damage due to excessive forces moving the member into contact with the guides and gates. Additionally, to align the receiver member in the plurality of orthogonal directions (e.g., the cross-track and in-track directions and remove skew), a complex arrangement is required where the various alignment actions take place sequentially with the member being handed off from one alignment element to the next. This results in a relatively extensive assembly which requires considerable time to accomplish the entire alignment function.
Several recent arrangements have been disclosed which address the reduction of the overall assembly for aligning a transported member in several orthogonal directions (i.e., the cross-track, in-track, or skew directions). U.S. Pat. No. 4,799,084 (issued Jan. 17, 1989, in the names of Koike et al) shows a transport roller assembly which is mounted such that at a selected time such roller assembly is movable by a cam and follower mechanism in a lateral direction to provide cross-track alignment. U.S. Pat. No. 4,805,892 (issued Feb. 21, 1989, in the name of Calhoun) shows a sheet transport assembly where a roller assembly pair is axially movable to bring an in-track edge of a sheet to a predetermined position for cross-track alignment. U.S. Pat. No. 5,078,384 (issued Jan. 7, 1992, in the name of Moore) describes an arrangement where selectably controllable drive rolls cooperating with sheet skew and lead edge sensors drive and deskew sheets. None of the apparatus disclosed in these patents accomplishes alignment of a transported member in all of the orthogonal directions as defined above.
U.S. Pat. No. 5,094,442 (issued Mar. 10, 1992, in the names of Kamprath et al) shows a registration apparatus having independent variable speed drive roller assemblies which are supported by an assembly movable transversely to the direction of sheet movement. While the apparatus of this patent can accomplish alignment of a transported member in the cross-track, in-track, and skew directions, it is of a complex nature requiring the entire apparatus to be moved in the transverse direction.